Electrical measuring instrument



May 3, 1938. l F, X. LAMB l 2,116,154

l ELECTRICAL MEASURING INSTRUMENT Filed July 1,5, 1936 mi lf .I

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. w-Sy Y o for flush mounting,

Patented May 3, 1938 PATENT OFFICE v ELECTRICAL' MEASUBING INSTRUMENTFrancis X. Lamb,

to Weston Newark, N. J.,

East Orange, N. J., assigner t Electrical Instrument Corporation,

a corporation of New Jersey Application July 15, 1936, Serial No. 90,806

3 Claims.

This invention relates to electrical measuring instruments, andparticularly to the casing., the terminals, and other structural detailsfor adapting the instruments for either flush or surface 5 mounting on apanel.

It is usual to provide soldering lugs for connecting leads to aninstrument of the flush `mounting type, and to provide threaded terminalstuds in the case of surface mounted instruments,

the terminal studs also-serving to support the instrument upon thepanel. The customary instrument designs do not permit of an alternativemounting of the instrument upon or flush with `the panel, and the usualpractice has been to manufacture two types of instrument casings inwhich 1a standard instrument movement may be mounted. Furthermore, sometypes of ammeters with internal shunts have been open to the objectionthat a slight relative movement of the terminal studs and shunt intightening nuts upon the studs to mount the instrument would result 'ina buckling or breaking of the shunt.

,Objectsof this invention are to provide electrical measuringinstruments having casings and terminals'of such design. that theinstruments are adapted for either flush or surface mounting upon apanel. An object is to provide instruments of the type stated in whichthe casing and terminal arrangements permit adaptation of the instrumentfor different types of lmounting without opening the instrument casing.A further object is to provide electrical measuring instruments,specifically ammeters having internal shunts, in which the shunts andterminal studs are of such mechanical design that al tightening stressupon the shun object of the -invention is to provide electricalmeasuring instruments having casings designed with threaded terminalinserts mounted in the base of the casing for 'receiving bolts. forattaching soldering terminals thereto or for receiving threaded terminalstuds; a

` masking shell being preferably `provided for im- 5 proving theappearance of the casing in the case of a surface mounting.. l

These and other objects and advantages of the inventio will be' apparentfrom the following specicstion when taken with the accompanying 'drawingin which:

on embodiment of the invention adopted for sash mountins on a panel;

Fig. 2 is a plan view of the same with parts` -u showninsectionzsndcover glass 8 of the shell i.

of nuts upon'the studs will not result in any More speciilcally, an

cannot be damaged `rthat are embedded in the m. 1 n o. nde view, withpms in section, of

Fig. 3 is a side elevation o f the same instrument mounted on thesurface of a panel. J

In the drawing, the reference numeral I identitles the cup-shaped shellwhich' is secured to the insulating base 2 by screws J to form thecasing 5 for an electrical measuring instrument which includes apermanent magnet 4 and a pivoted coil 5. The coil carries a pointer 6which is displaced over a scale plate 1 that is visible through the Theinstrument parts lo are supported upon the base 2 in known manner, andthe structural details of these parts and their mounting are notessential features of the invention.

The casing or flange 9 to adapt the same for flush mounting on a panelil by a clamping ring I i or the like. Terminal inserts are anchored inthe base 2 to adapt the instrument for flush mounting or aiternativelyfor surface mounting. The inserts 2 have threaded shanks i2 extendinginto the casing and non-circular portions i3, preferably of squarecross-section, embedded in the base 2 to, prevent rotation of theinserts. Circular portions Il at opposite sides of the squared sectionIl pro. 25 vide flat connector-receiving surfaces that are approximatelyflush with but preferably just outside the planes of the opposite facesof the base 2. The embedded section of the insert has a threaded bore I5elements for connecting the instrument to an ex'- ternal circuit. Asshown in Fig. 1, thesel connections take the form of terminal lugs I8which are secured to the inserts by bolts I1 and lock washers Theillustrated instrument is an ammeter hav- 35 ing an internal shunt i! ofthe usual strip type which has terminal lugs 2l for mounting the same onthe shanks i2 ofthe terminal inserts. The leads 2l to the instrumentmovement are 40 secured to the lugs of the shunt inthe usual manner andthe shunt is secured to the shanks i2 o! the inserts by nuts 22 and lockwashers 23. Attention is directed to the fact that the shunt bytightening the bolts I1 45 into the inserts since the inserts areanchored against rotation by the non-circular portions Il base 2 duringthe forbillty of damage which is present when the shunt is mounted vonterminal' shanks which extend through openings inl the base .and aresecured in place`by, nuts. No excess torque on the termishell I Ahas anouter peripheral 15 for receiving the appropriate 30 nal inserts, shortof that which destroys the base 2, will result in'a stress on the shunt.

'I'he instrument shown in Figs. 1 and 2 is also adapted for surfacemounting on a panel merely by the substitution oi' another type oi'terminal connection and, preferably, a masking shell. 'I'his type ofmounting is illustrated iii Fig. 3. Studs 24 are threaded into the boresI5 of the inserts and are locked in place by nuts 25 and lock washers26. The studs 24 extend through a panel I' and receive nuts 21 fordrawing the casing shell I against. a masking shell 28- that has aninner end seated against the panel and an outer endfor engagement withthe iiange S of the shell i.v 'I'he terminal lugs or straps 28 forconnecting the instrument into an external circuit are secured to thestuds 24 by nuts 30. I'he masking shell 28 is not essential in the caseof surface mounting, but is desirable to avoid an unsightly gap betweenthe instrument casing and the panel when, for a rigid mounting, thestuds 24 are anchored to the terminal inserts by the nuts 25.

Instruments such as illustrated may be kept in stock for use either asflush or surface mounted instruments. It is not necessary to open theinstrument casing to adapt Vthe instrument for either type of mounting.Bets of bolts I1 and terminal lugs I6 may be kept in' stock for illlingorders for flush mounted instruments, and sets of studs 2,4 and shells28 for nlling orders for surface mounted instruments. These parts are ofsmall bulk and are equally applicable to either voltmeters or ammeters,and to instruments ofv diierent ranges and electrical design.

It is to be understood that the invention is not restricted to theparticular constructions herein shown and described. and various changesin the design, size and relation oi the various parts may be madewithout departing from the spirit of my invention as set forth in thefollowing claims.

Iclaim:

`for surface mounting `an insulating base and 1. An electrical measuringinstrument comprlsing a casing having a base and an outer peripheraliiange adapting the same for iiush mounting on a panel, an instrumentmovement within said casing, terminal inserts carried' by said base andhaving threaded bores presented towards the exterior of the casing,mounting studs threaded into said inserts and carrying nuts, and amasking shell adapting said casing on a panel, said shell havseatingrespectively against flange and a panel when the are passed throughopenings in ing opposite ends for said peripheral mounting studs thepanel.

2.- An electrical measuring instrument for mounting on a panel, saidinstrument comprising a casing having an insulating base and an outerflange adapting the casing for ilush mounting on a panel, an instrumentmovement mounted on said base, terminal means anchored in said base, andmeans including a masking shell for the surface mounting of the casingon a panel; said shell having ends for seating against said flange and apanel to enclose the casing and space the same from the panel.

3. An ammeter comprising a casing having an outer ange adapting thecasing for flush mounting, an instrument movement mounted on said base,a pair of terminal inserts anchored in said base, said inserts havingthreaded shanks within said casing and threaded bores presented towardsthe exterior thereof, la shunt mounted on the threaded Shanks o! saidinserts, and means for mounting said casing on the surface of a panel;said mounting means comprising studs threaded into said inserts andadapted, to pass through the panel, and a masking shell enclosingsaidcasing and having ends for seating against said outer ange and thethe casing from the panel.

FRANCIS X. LAMB.

panel to space the base of 4D

